Three-parent embryo

Is it squeamishness or superstition that makes the announcement from Newcastle University of plans to create a “three-parent” embryo controversial? I cannot see a profound difference between this kind of “non-natural” method of conception and any of the plethora of IVF and related treatments. They’re all non-natural when compared to the conventional approach to conception, after all.

However, the potential benefits of this new approach could be immense, when considered from the perspective of mitochondrial disease, which it seeks to prevent. So, what’s it to be non-natural and healthy or natural and not?